The feds have a top Manhattan hand surgeon on board to help nail a doctor at the heart of the Long Island Rail Road “gravy train” pension scam.

Dr. Alton Barron — longtime orthopedic surgeon for the New York Philharmonic orchestra and the Metropolitan Opera — is slated to serve as an expert witness against Dr. Peter Ajemian, according to court papers filed yesterday.

Barron is prepared to testify that Ajemian “frequently and improperly” diagnosed railroad workers with career-killing disabilities based on “independently meaningless” tests, such as MRIs and X-rays, the Manhattan federal court filing says.

Barron will also say that Ajemian “generally did not provide or offer his patients any meaningful treatment for their purported conditions, although most of these conditions . . . are entirely treatable to the point where the patient can return to work at 100 percent capacity,” prosecutors wrote.

“Dr. Barron will illustrate his opinions, and the basis for his opinions, by reference to particular diagnostic tests and patient files.”

Barron is co-author with his wife, psychoanalyst Carrie Barron, of “The Creativity Cure: A Do-It-Yourself Prescription for Happiness,” which includes a contribution from Bruce Springsteen and was endorsed by former KISS drummer Peter Criss.

Ajemian, his former office manager and several LIRR retirees go on trial in February.